Digital printing machines may include platens, or pallets, on which items to be printed, such as garments or other textiles, are positioned for printing. Examples of such printing machines are the machines manufactured by Kornit Digital, Ltd.
The conventional platens used in known digital printing machines are formed as substantially flat beds, i.e., having a substantially horizontal upper surface area. These conventional platens provide acceptable results when used for printing on items, such as T-shirts, that have substantially uniform horizontal surface areas. However, conventional direct on-garment digital printing machines, on which the print heads and platen are vertically fixed with respect to each other, tend to produce unacceptable print quality when printing on garments, such as golf shirts, that have raised portions, such as plackets, collars, hems, or pockets. This is due at least in part to the fact that the print heads are positioned at a fixed height above the surface of the garment.
FIGS. 1 and 2 illustrate an example of a conventional digital printing machine 1 having a print head 2 and a platen 4 having a top printing surface 5. The print head 2 is positioned at a fixed vertical position relative to the platen 4, and includes one or more nozzles 2a configured to spray ink 3 to print a design or image on an outer surface of a textile or garment 6. By “fixed vertical position”, we mean that the print head 2 does not move in vertical direction relative to the platen 4. The upper surface 5 is substantially flat (horizontal) with no deviation in surface height. As shown in FIG. 1, the surface 5 supports the textile or garment 6 such that the textile or garment 6 has a substantially uniform thickness or height, T. Thus, the garment has a uniform horizontal printing surface 9, which receives a substantially uniform ink spray pattern P from the nozzle 2a. 
In FIG. 2, the platen 4 supports a textile or garment 8 having a variable thickness or height. Specifically, the garment 8 includes a first area 8a having a height Ta, and a second, raised area 8b having a height Tb that is greater than the height Ta. As can be seen in FIG. 2, the raised area 8b causes the garment 8 to have a non-uniform horizontal printing surface 9a, which in turn results in an irregular spray pattern P1 from the nozzle 2a. As will be appreciated, the irregularity in the spray pattern P1 diminishes the quality of the design or image printed on the garment 8.
Some known printing machines address the problem of printing on variable height garments by providing mechanisms for adjusting either the vertical position of the platen or the vertical position of the print heads when there is a variation in the height of a particular article. However, providing such vertical position adjustment mechanisms can add significant complexity and expense to printing machines.
In view of the above, it is desirable to provide a simple, cost-effective solution for digitally printing on garments of variable height with printing machines having vertically-fixed print heads.